In November 1986, US Representative Dan Lungren stood in an ornate room in the White House, beaming as President Ronald Reagan signed a bipartisan immigration bill plucked weeks earlier from certain death.

The bill legalized the largest number of immigrants in US history and, for the first time, made it a crime to knowingly hire unauthorized workers. But the celebration ended there: Over the next three decades, ­illegal immigration soared in Massachusetts and most other states.

“There was no enforcement,” Lungren, a Republican who lost his California seat in the House last year, said in a recent interview. “And I mean literally, no enforcement.”

Now enforcement is again a pivotal issue as Congress braces for another roller coaster immigration debate and hard questions about the government’s plans to stem illegal immigration. A bipartisan Senate group is crafting a bill, expected as soon as Thursday, that would create a path to citizenship, reduce backlogs for family and work visas, and end the hiring of unauthorized workers.

Senator Charles Grassley, an Iowa Republican and ranking member of the Senate Judiciary Committee, said he has warned his colleagues that enforcement must come first. He voted for the 1986 act only to watch illegal immigration in ­Iowa catapult from 5,000 in 1990 to 75,000 in 2010, according to the Pew Hispanic Center.

“I want immigration reform, but the point is that the advocates for immigration reform are the ones that want to make everything real easy,” Grassley said. “Well, it ain’t gonna be easy.”

But supporters of immigration overhaul say the only way to make enforcement of laws feasible is to offer a path to citizenship to the estimated 11 million immigrants now in the country illegally, nearly four times the number legalized by the 1986 law.

‘We understand that this is going to be difficult, but this is the time to find a solution, now, once and for all.’

“We understand that this is going to be difficult, but this is the time to find a solution, now, once and for all, not piecemeal,” said Rocio Saenz, president of SEIU Local 615, a labor union. The number of immigrants illegally in Massachusetts has nearly tripled since 1990 to 160,000, according to the Pew Hispanic Center.

The US government increased enforcement in the late 1990s, and especially after the 2001 terrorist attacks, building a massive enforcement infrastructure that includes prisons, border fences, and high tech systems designed to detect illegal immigrants. The Migration Policy Institute reported recently that the government spent nearly $18 billion on enforcement last year, more than on the main federal criminal law enforcement agencies combined.

“We have never had this level of border security,” said ­Muzaffar Chishti, a lawyer and an author of the report.

Still, some say that measures needed to control illegal immigration are not in place — measures such as a nationwide system for employers to check workers’ immigration status, more frequent audits of companies that hire unauthorized workers, and a fingerprint system to track people who overstay visas. According to a 2006 Pew Hispanic Center report, visa overstayers and other legally admitted visitors accounted for as many as 50 percent of immigrants here illegally.

“I would vote for an amnesty if it were definitely an amnesty that dealt with the problem so that we don’t have another 11 million illegal aliens,” said Mark Krikorian, executive director of the Center for Immigration Studies, a think tank that favors stricter controls on immigration. “Nobody believes that’s going to happen.”

For example, advocates on both sides of the issue expect that any immigration law would mandate nationwide use of E-Verify — an electronic system for employers to check workers’ legal papers.

But it is unclear if the program, which is mandatory to varying degrees in several states, can expand nationwide soon.

Steve Blando, a spokesman for US Citizenship and Immigration Services, said the agency would implement E-Verify across the country if Congress mandated it. But he could not say how much that would cost.

“We cannot estimate a cost for mandatory E-Verify without specific legislation to model the costs,” Blando said. He said the agency sought more than $100 million to run E-Verify this year alone for just 7 percent of the nation’s employers
.

Tracking people who overstay their visas is another challenge. The 9/11 Commission recommended that Homeland Security create a biometric entry-exit system to track visitors after the 2001 attacks revealed that some of the airplane hijackers had overstayed their visas. But almost nine years after the report, the program’s cost and timeline remain unclear.

Homeland Security takes biometrics, such as fingerprints, of foreigners who enter the United States, but not when they leave. Instead, to find visa overstayers, Homeland Security checks flight manifests and other records. More than 450 immigration agents then work to catch tens of thousands of visa overstayers each year, focusing first on people who present a threat to public safety.

Finally, the 1986 sanctions that were supposed to compel companies to check workers’ papers never materialized enough to significantly deter the hiring of illegal immigrants.

Fines levied against companies increased from $1.6 million in 1999 to $12.4 million in 2012, according to Immigration and Customs Enforcement, but prosecutions were far less common. In fiscal 2012, officials arrested 240 managers and some 150 were convicted.

ICE spokesman Brandon Montgomery
said the number of employer arrests has risen substantially in recent years. “It is important to highlight that these cases take time to develop and to come to fruition.”

While many fault the 1986 act for the lack of enforcement, the law’s bipartisan champions in Congress say much of the criticism was unfair.

Former US representative Ron Mazzoli, a Kentucky Democrat, and former senator Alan Simpson, Republican of Wyoming, said the US government failed to consistently fund enforcement until it was too late.

Now, Simpson said, the government needs to legalize immigrants in the country, provide enough work visas to meet the demand for labor, and have a secure identification to prevent the use of fraudulent work documents.

“Your option if you want to do nothing is to just watch a very unfortunate group of people who are here, they’re illegal and they’re expendable and they’re used and abused,” Simpson said
. “What do you want to do — go find them and deport them? Come on.”